The present invention is directed generally to machinery for plastic container production and specifically to an apparatus for trimming a flange on a cylindrical opening of a blow molded plastic container.
Due to economic considerations, wide mouth blow molded containers are currently manufactured by employing standard small mouth preforms. With these preforms, a blown container having a narrow dome portion expanding to a wider dome portion connected to the mouth of the wide mouth container is initially formed. Then the dome portion is removed, leaving the wide mouth container. This process is advantageous because standard small mouth preforms are manufactured in the hundreds of millions and are inexpensive. In contrast, use of special wide mouth preforms for each new container design would be significantly more expensive. Thus, there is a considerable economic advantage in use of standard small mouth preforms in the manufacture of wide mouth blow molded containers.
The current manufacturing process for wide mouth blow molded containers can be explained with the aid of FIGS. 1 and 2. FIG. 1 illustrates a typical wide mouth blow molded container 100 in the as-blown condition, while FIG. 2 illustrates several steps in the manufacture of a wide mouth container. The bottle 100 comprises two portions, a body portion 102 and a dome portion 104. Separating the body portion 102 and the dome portion 104 is a radially inwardly extending circumferential trim line groove 106. Below the trim line groove 106 is a trim scrap ring 108, which comprises the desired outer flange 110.
As in the manufacture of small mouth blow molded containers, the first step is a preliminary trimming step in which the dome portion 104 is removed (FIG. 2b). However, to complete the wide mouth bottle, an additional trimming step is required to remove the trim scrap ring 108 and form the outer flange 110 (FIG. 2c). Because, an outer flange is required, the prior art reverse punch method cannot be used. Further, use of the ream method is undesirable because of the likelihood of scattered chips entering the container.
Methods of trimming external flanges are known in the can making art. In one conventional method, the can is first mounted on a rotating vacuum chuck. The chuck is then advanced until the can abuts a rotating main disc cutter. To cut the flange, a rotating auxiliary disc cutter located below the flange is advanced until it pierces the flange. In this system, the vacuum chuck, the main disc cutter and the auxiliary disc cutter are all independently driven and must be carefully coordinated to ensure a quality cut surface. To further improve the quality of the cut and aid in scrap ring removal, the auxiliary disc cutter is advanced at an angle to the axial direction of the can. This apparatus and method is suitable for trimming the flanges of a metal can. However, trimming a plastic blow molded bottle with this apparatus and method results in a flange with numerous burrs and slivers.
The prior art methods of trimming an inner flange on a blow molded container are either inappropriate for trimming an outer flange, expensive, have undesirable side effects or result in poor quality flanges. Thus, it would be desirable to have an apparatus and method of trimming an outside flange that was efficient, inexpensive, had no deleterious side effects and produced a reliable high quality flange.
The present invention includes a trim station for trimming a flange of a container comprising a rotating primary knife and a secondary knife mounted on a movable member, wherein the secondary knife is moved into a cutting position by advancing the movable member in a direction parallel to an axial direction of the container.
In another aspect of the invention, the present invention also includes a trim station as noted above, further comprising a centering cone adapted to center the container on the rotating primary knife.
In another aspect of the invention, the present invention also includes a trim station as noted above, further comprising a spindle assembly having a cam and a cam follower, wherein the spindle assembly is adapted to raise the container to the centering cone.
In another aspect of the invention, the present invention also includes a trim station as noted above, wherein the secondary knife is frictionally driven by the primary knife.
In another aspect of the invention, the present invention also includes a trim station as noted above, further comprising a trim ring ejector plate to remove a trimmed flange from the trim station.
In another aspect of the invention, the present invention also includes a trim station as noted above, further comprising a moving mechanism to advance the movable member.
In another aspect of the invention, the present invention also includes a trim station as noted above, wherein the moving mechanism is selected from a group consisting of a pneumatic mechanism, a mechanical mechanism and an electrical mechanism.
In another aspect of the invention, the present invention also includes a trim station as noted above, wherein the moving mechanism further comprises a spring adapted to hold the secondary knife in a cutting position.
In another aspect of the invention, the present invention also includes a trim station as noted above, further comprising a cut adjustment mechanism to adjust the depth of the cut.
In another aspect of the invention, the present invention also includes a trim station as noted above, wherein the rotation axes of the primary knife and the secondary knife are offset.
In another aspect of the invention, the present invention also includes a trim station as noted above, wherein the offset is from 1 mm to 12 mm.
In another aspect of the invention, the present invention also includes a trim station as noted above, wherein the offset is from 5 mm to 9 mm.
In another aspect of the invention, the present invention also includes a trim station as noted above, wherein the offset is 7 mm.
The present invention also includes an apparatus for trimming a flange of a container, comprising a plurality of trim stations, wherein each trim station includes a rotating primary knife and a secondary knife mounted on a movable member and the secondary knife is moved into a cutting position by moving the movable member in a direction parallel to the axial direction of the container.
In another aspect of the invention, the present invention also includes the apparatus as noted above, wherein the plurality of trim stations are mounted on a rotating trim turret.
In another aspect of the invention, the present invention also includes the apparatus as noted above, further comprising an infeed starwheel for supplying containers to a trim station.
In another aspect of the invention, the present invention also includes the apparatus as noted above, further comprising a discharge starwheel to transfer a container from a trim station out of the apparatus.
In another aspect of the invention, the present invention also includes the apparatus as noted above, further comprising a pretrim station.
In another aspect of the invention, the present invention also includes the apparatus as noted above, wherein the pretrim station is configured to remove the dome portion of a plastic bottle.
The present invention also includes a method of trimming the flange of a container comprising the steps of loading a container with a flange on a container holder of a spindle assembly, advancing the container toward a primary knife by advancing a spindle in the spindle assembly, advancing a secondary knife in a direction substantially parallel to an axial direction of the container until it penetrates the flange of the container; and cutting the flange until the flange is completely severed from the container.
In another aspect of the invention, the present invention also includes the method above, further comprising a step of adjusting the depth of penetration of the secondary knife into the flange of the container.
In another aspect of the invention, the present invention also includes the method above, further comprising the step of centering the container on a centering cone affixed to the primary knife.
In another aspect of the invention, the present invention also includes the method above, wherein the step of cutting comprises rotating the container.
In another aspect of the invention, the present invention also includes the method above, wherein the primary knife is driven and the container rotates by frictional contact with the primary knife.
In another aspect of the invention, the present invention also includes the method above, wherein the container holder is rotatably mounted with bearings on the spindle.
In another aspect of the invention, the present invention also includes the method above, wherein the container holder rotates by frictional contact with the container.
In another aspect of the invention, the present invention also includes the method above, wherein the frictional contact is maintained by springs in the spindle assembly.
In another aspect of the invention, the present invention also includes the method above, wherein the secondary knife is frictionally driven by contact with the flange of the container.
In another aspect of the invention, the present invention also includes the method above, wherein the primary knife, the container and the secondary knife rotate at essentially the same speed.
In another aspect of the invention, the present invention also includes the method above, wherein the step of advancing the container comprises rotating the spindle assembly over a stationary cam.
In another aspect of the invention, the present invention also includes the method above, wherein the step of advancing the secondary knife is performed with a moving mechanism.
In another aspect of the invention, the present invention also includes the method above, wherein the moving mechanism is selected from the group consisting of a pneumatic mechanism, a mechanical mechanism or an electric mechanism.
In another aspect of the invention, the present invention also includes the method above, wherein the secondary knife is held in a cutting position by a spring.
In another aspect of the invention, the present invention also includes the method above, wherein the secondary knife is withdrawn to a non-cutting position by the moving mechanism.
In another aspect of the invention, the present invention also includes the method above, wherein a rotation axes of the primary knife and the secondary knife are offset.
In another aspect of the invention, the present invention also includes the method above, wherein the offset is from 1 mm to 12 mm.
In another aspect of the invention, the present invention also includes the method above, wherein the offset is from 5 mm to 9 mm.
In another aspect of the invention, the present invention also includes the method above, wherein the offset is 7 mm.
The present invention also includes a spindle assembly for use in a flange trimming apparatus comprising a spindle, and a container holder mounted on bearings on a first end of the spindle, wherein the container holder is adapted to be freely rotatable.
In another aspect of the invention, the present invention also includes the spindle assembly above, further comprising a cam and a cam follower affixed to a second end of the spindle to advance the spindle.
In another aspect of the invention, the present invention also includes the method above, further comprising springs between the container holder and the spindle.
The present invention also includes a container made by the process above.
In another aspect of the invention, the present invention also includes the container above, wherein the container is plastic.
In another aspect of the invention, the present invention also includes the container above, wherein the container is free of burrs or slivers.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.